1. Field of the Invention
The present invention relates to a method for producing a deposition mask, that includes forming of an opening pattern at a predetermined position in a resin film by laser processing so as to penetrate therethrough, and more particularly, relates to a method for producing a deposition mask enabling high-speed laser processing.
2. Description of Related Art
In conventional methods for producing a deposition mask, a first resist pattern having a plurality of openings is formed on a metal plate, an etching process is performed via the openings of the first resist pattern to form a plurality of opening patterns on the metal plate, the opening patterns penetrating through the metal plate, the first resist pattern is then removed, a second resist pattern having a plurality of second openings, through each of which a metal edge portion having a predetermined width around the corresponding opening pattern is exposed, is formed on the metal plate, an etching process is performed via the second openings of the second resist pattern, to form a mask main body portion around the plurality of openings and a peripheral portion having a thickness greater than that of the mask main body portion and positioned around the mask main body portion, and then the second resist pattern is removed (for example, see Japanese Patent Application Laid-open Publication No. 2001-237072).
However, in such conventional methods for producing a deposition mask, the plurality of opening patterns is formed on the metal plate so as to penetrate through the metal plate, by subjecting the metal plate to a wet etching process. Accordingly, highly precise opening patterns cannot be accurately formed by isotropic etching in the wet etching. Particularly, for example, in a case of a deposition mask for an organic EL display panel having a large area with a side length of tens of centimeters, opening patterns of the entire mask surface cannot be uniformly formed due to the generation of etching unevenness.
The inventors suggest a composite-type deposition mask having a structure in which a resin film having opening patterns which are formed corresponding to thin film patterns to be deposited on a substrate and have the same shape and dimensions as those of the thin film pattern, and a thin plate-shaped magnetic metal member having through holes formed to include the opening patterns therein are brought into close contact with each other.
The composite-type deposition mask is a deposition mask in which opening patterns are formed by laser processing on a thin resin film having a thickness of approximately 10 μm to 30 μm. It has advantages in that highly precise opening patterns can be accurately formed and the opening patterns can be uniformly formed over the entire mask surface even in a case of a deposition mask having a large area as described above.
In order to increase the speed of laser processing, increasing a laser output is effective. However, when the laser output is increased, the intensity distribution of laser beams becomes non-uniform, and due to the non-uniformity of the intensity distribution, the frequency of generation of a cutting remainder (hereinafter, referred to as “burr”) on an edge portion of an opening pattern is increased.
There is a concern that the burr may form a shadow of the deposition and thereby cause shape disorder of the edge portion of the thin film pattern to be formed by deposition, or the burr may form a gap between the deposition mask and the substrate for film deposition, and thus a film deposition material may easily enter into a portion below the mask, so that the area of the thin film pattern may be increased.
As a measure for avoiding this problem, a method including: forming a hole portion having a thin layer remaining in a bottom portion thereof by laser processing; and then penetrating the bottom portion of the hole portion by etching, is also considered, but there is a concern that the process of producing a deposition mask may be made complicated.